As the two-case type portable radio apparatus in the prior art, the folding portable radio apparatus in which the antenna formed of a plate-like conductor is connected to an end portion of the first circuit board in the first case on the opposite side to the hinge portion that joins relatively movably the first case and the second case is known.
FIGS. 10(a),(b) are views showing a configuration of the portable radio apparatus in the prior art, and only a pertinent portion is shown herein. In FIGS. 10(a)(b), 2 is a first circuit board arranged in a first case 1, and a monopole antenna 6 formed of the above plate-like conductor is connected to an end portion of the first circuit board 2.
According to such portable radio apparatus, when an electronic parts 10 containing a built-in metal exists in a second case 3, a space in which no neighboring metallic substance is provided around the monopole antenna 6 must be created by expanding the first case 1 toward the opposite side to a hinge 5 along the longitudinal direction, as shown in FIGS. 11(a)(b), to ensure an operation of the monopole antenna 6 fitted to the first circuit board 2, and thus the antenna characteristic must be attained.
Also, as another two-case type portable radio apparatus in the prior art, as shown in FIGS. 12(a)(b), the folding portable radio apparatus in which the monopole antenna is provided to an end portion of the first circuit board 2 in the first case 1 on the opposite side to the hinge 5, which joins the first case 1 and the second case 3 turnably, and a resonance circuit 13 for cutting off a predetermined frequency is provided in the middle of the element has been proposed.
Such portable radio apparatus in the prior art is constructed as follows. The monopole antenna connected to an end portion of the first circuit board 2 is constructed by an element 11 and an element 12, the resonance circuit 13 for cutting off a predetermined frequency is provided in the middle, and the antenna having the impedance every frequency band is constructed.
In such portable radio apparatus, since a resonance band can be extended in addition to the resonance band obtained by the portable radio apparatus in FIG. 10 and FIG. 11, a multi-band radio communication utilizing different frequency bands can be accomplished. However, when the electronic parts 10 containing the built-in metal exists in the second case, a space in which no neighboring metal is provided around the element 11 and the element 12 must be created by expanding the first case 1 toward the opposite side to a hinge 5 along the longitudinal direction, as shown in FIGS. 13(a)(b), and thus the antenna characteristic must be attained.